This invention relates to tufting machines and more particularly to apparatus for shifting the needles transversely relatively to the backing material between the longitudinal rows of tufted pile formed by the machine.
The art of tufting incorporates a plurality of yarn carrying space needles extending transversely across the machine and reciprocated cyclically to penetrate and insert pile into a backing material fed longitudinally beneath the needles. During each penetration of the backing material a row of pile is produced transversely across the backing. Successive penetrations result in a longitudinal row of pile produced by each needle. This basic method of tufting limits the aesthetic appearance of tufted carpet so produced.
Consequently, methods have been devised which effect relative shifting between the needles and the backing material that provide patterning effects and that break up the noticable alignment of the longitudinal rows which detract from the appearance of the product. Such patterning means generally referred to as needle shifting or stitch placement drives generally are either driven by a rotating cam, a programmable fluid driven device, or a programmable indexing apparatus for drivingly engaging the needle bar to effect displacement thereof. Because the cam driven type is simple, inexpensive and reliable, it has been and remains the most popular drive system.
A drive rod connects the pattern cam drive system to a mounting plate for transversely driving the needle bar. Heretofore, as illustrated in my co-pending U.S. application Ser. No. 253,800 filed Apr. 13, 1981, and assigned to the same Assignee as the present invention, the drive rod was directly connected to a cam follower mounting rod journalled in bearing blocks and extending across and in front of the face of the pattern cam. With this construction, the mounting rod is driven by the followers as determined by the information on the periphery of the cam. However, one disadvantage of this system is that when a pattern change is desired, the follower mounting rod together with the follower must be removed to permit exchange of pattern cams. Consequently, the time required for making a pattern change is substantial.
Moreover, each time a change in cam was effected the needle bar would move slightly so that the relationship of the needles to the hooks and loopers was changed, thereby requiring additional time to effect a pattern change.
Recognizing the need for rapid change of the pattern cam, recent developments have devised various cam mounting systems permitting the cam to be readily replaced. No such developments, however, have been directed toward locking the needle bar during such cam changes to maintain the needle to hook relationship.